serial: msm_geni_serial: Reduce stale delay added in stop_rx_sequencer

Currently driver calculating stale delay based on baud rate during
stop_rx sequencer. When BT started with lower baud rate like 2400
this logic will add around 130msecs of extra delay during BT INIT.

This change will remove logic for stale delay calculation
based on baud rate and add constant delay of 10msec to
wait for stale interrupt during stop_rx_sequencer.

Change-Id: I566d79145ba887de71482642655b63c5bd640fc8
Signed-off-by: Yatish Kumar Singh <yatishku@codeaurora.org>